I suspect what did in Arimaa in 2015 as far as humans vs. computers was
that besides that a computer could be programmed for tactics no human could
normally see (e.g. bringing a rabbit to the final rank when already
somewhat close to it, securing instant victory, as done within even a small
number of ply), programming effective heuristics to take advantage of by
now well-known advice (to Arimaa players) on strategies used by humans must
have finally been achieved.

In Go I understand there are many rules of thumb, or heuristics, about what
constitutes best play in local (e.g. corner) situations, at least in the
opening phase of the game. Though I am a duffer at Go (as opposed to chess,
at least some might say), I understand that for tactical considerations
'liberties' is a vital concept (i.e. how many empty points are next to the
whole perimeter of a group of stones). That would be something to strive to
optimize. Then for Go strategy there are also at least a handful of really
grand concepts that are more difficult to program for computers, I would
imagine; in short, a skilled human can at times see the strong influence
exerted on territory and group(s) of stones by one or more stones for a
long time to come. Also, good Go players can get a rough count during the
middlegame phase of how much territory each player can expect to end up
with, if neither side sooner or later tries to initiate a risky tactical
melee, it seems.

For those who may think that Go is rather dull, I wondered that too. In
talking to a friend who spent some time in Japan and became somewhat
skilled at Go (and Shogi), he told me that these days the top country at Go
is South Korea. Apparently there are at least two fundamental styles at Go,
similar to in standard chess. In Go one can play to win quietly by mostly
winning on territory (like strategically played chess) or one can play to kill one or
more large groups of stones, taking many prisoners and territory if
successful, and likely inducing the opponent to resign earlier than near
the endgame phase (like tactical attacking chess). The South Koreans apparently all
like to play in such an aggressive attacking style.

Speaking of strategy, I can mention that for Sac Chess there could still be
weak pawns that appear, as well as players being left with just one bishop
at some stage (and perhaps then weak on squares of the opposite colour), so
there are at least these elements of strategy that may carry over from
standard chess to some degree. I would also note that in Sac Chess if a
player would avoid making an early big mistake, his king may be well
defended by all the extra pieces near it, even if they are doing little
else for a long time to come. This is one important difference that there
may be between Sac Chess and (say) Alekhine Chess, even though the latter
may also apparently have a little too much piece firepower for some folks
to like too.